The present invention relates in general to sewing machines and in particular to a new and useful sewing machine with a step motor operated feed device which utilizes a feed wheel disposed next to a stitch formation point and which is driven synchronously with stitch formation tools, the feed wheel being driven by a step motor.
In a known sewing machine of this kind (U.S. Pat. No. 2,275,716), the drive of the feed wheel occurs from the main shaft of the sewing machine via a stepping mechanism which imparts an intermittent feed movement to the feed wheel. For continuously variable adjustment, such a stepping mechanism must be designed as a clamping mechanism with a free-wheeling coupling. Due to their frictional entrainment, such stepping mechanisms are very inaccurate, and besides, they cannot be used for driving in a reverse direction. Especially at varying speeds of a sewing machine, because of the large inertial mass of the mechanical transmission parts, there results a considerable slip in the drive transmission and hence considerable deviation of the executed stitch length from the set value. Backward sewing is not possible at all with this sewing machine.